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FORMATION OF SPATIAL REVERSAL LEARNING SETS IN RATS: COMPARISON OF INSTRUMENTAL AND AUTOMAINTENANCE PROCEDURES
Citation:
Bushnell, P. AND M. Stanton. FORMATION OF SPATIAL REVERSAL LEARNING SETS IN RATS: COMPARISON OF INSTRUMENTAL AND AUTOMAINTENANCE PROCEDURES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/022 (NTIS PB92143940), 1991.
Description:
Spatial discriminations were acquired by rats through repeated pairings of the retraction of a response lever with food; serial reversals of these discriminations were used to generate an automaintained reversal learning set. This learning set was compared to that obtained with a similar procedure which included an instrumental response-reward contingency. In the automaintenance (AU) procedure, rats received food after every retraction of a "positive" response lever (S+); a second, "neutral" lever (So) was presented on an identical schedule, except that retraction of the So occurred randomly with respect to food delivery. Responses to the S+ were elicited at fairly constant.rates during daily 100-trial conditioning sessions. Responses to the o occurred early in each session but rapidly diminished across trials. When the valences of the levers were reversed, responding shifted to the new S+ and diminished n the new So. Criterion for reversal was defined as a discrimination ratio (DR) of t least 90% responding to the S+ in two consecutive 10-trial blocks. With repeated reversal acquisition of criterion performance occurred with increasing rapidity, demonstrating the reversal learning set phenomenon. A second group of rats was rained on a similar instrumental schedule, on which at least 1 response to the as required for food delivery. Response rates in this instrumental (IN) group were approximately double those of the AU group; nevertheless, relative rates of S+ and responses were similar to those of the AU group, reversals were acquired at about the ame rate, and the learning sets generated were qualitatively and quantitatively similar. Small differences in' learning sets were observed: the AU group acquired the first reversal more quickly than the AU group, while asymptotic reversal performance as slightly better in the group compared to the IN group. This method may hold promise as a tool for the study of learning, both in terms of acquisition of spatial reversal learning sets and of repeated acquisition of spatial reversals.